1. Field of the Invention
The present invention relates to a private branch exchange system and a caller number notification method using the same, and in particular, to a private branch exchange system for notifying an extension telephone set in a private branch of information transmitted from a public network to a private branch exchange system and a caller number notification method using the same.
2. Description of the Related Art
Hitherto, a service has been provided that allows a receiver's telephone set to display the telephone number of a caller's telephone set. The service enables the telephone number of a caller's telephone set to be displayed on the receiver's telephone set by providing analyzing means which analyzes the telephone number information of a caller's telephone set that is received in an exchange and is transmitted to the receiver's telephone set by the exchange and then is received by the receiver's telephone set and display means which displays the analyzed telephone number.
However, a private branch exchange that is installed at a private branch in a workplace does not have a function for notifying the number of a caller, that is transmitted from a public network, to the extension telephone set of a receiver. For this reason, a caller's number cannot be displayed on the extension telephone set.
JP-1999-041359A discloses a method in which a dedicated modem for notifying a private branch exchange of a caller's number and a database for storing caller's numbers are provided to notify an extension telephone set of a caller's number stored in the database.
However, the method disclosed in the above patent document requires storing caller's numbers in a device of the private branch exchange. Using a large scale device controlled by a plurality of control blocks causes a problem in which an incoming call signal transmitted to an extension telephone set cannot be synchronized with the stored caller's numbers during transmission timing.